The present invention relates to an AC electrical power supply system, comprising a back-up power supply equipped with an inverter operating in reversible mode.
It is state of the art to equip a system supplying power to a load with a back-up power supply capable of provisionally replacing the main power supply, whether it be single or multi-phase, in the event of failure of the latter. This back-up power supply uses the power supplied by a bank of batteries. This battery bank supplies a reversible inverter which operates, in both directions, as a voltage generator. In the event of a mains power supply failure, the load is automatically disconnected by a static contactor provided for this purpose, and it is then the back-up power supply which supplies, via its inverter, the AC electrical power to this load. The inverter being energized in reversible mode, it is via the latter that the battery is recharged by the mains power supply when, everything having reverted to normal, it is again supplying the load.
In systems of this kind, a dephasing inductance is generally connected between the above-mentioned static contactor and the load, in order to obtain an inverter current and voltage in phase, when the batteries are recharged via the reversible inverter (U.S. Pat. Nos. 4,673,825, and 4,238,691). This solution has the drawbacks of both increasing the cost price of the system, and of causing a relatively high current to flow in the inverter when, being on stand-by, its only function is to act as the battery recharging circuit.